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Biomedical subjects

H Richter

Publications and source records attributed to H Richter.

At least 145 records · Page 8Linked to original sources
PubMed1985

Fibrinmonomer binding to macrophages mediated by fibrin-binding fibronectin fragments.

Binding of 125-I-fibrinmonomer to peritoneal macrophages was investigated in dependence of plasma fibronectin and of its thrombin- or plasmin-derived fragments. Plasma fibronectin failed to enhance cell binding of 125-I-fibrinmonomer. In contrast, 30kD-fragments derived from the N-termini of the fibronectin subunits improved binding considerably. The association with the cell surface was completely inhibited by EDTA, 2-5 mM putrescine and to about 40 per cent by 0.1 mM dansylcadaverine suggesting that a transamidase-catalyzed cross-linking reaction was involved. Thrombin-derived 200kD-remnants of the fibronectin subunit chains failed to mediate cell binding of 125-I-fibrinmonomer provided they had been deprived of residual thrombin activity. Otherwise they were active and their activity was inhibited by the thrombin inhibitor hirudin. Plasmin-derived 200 kD-fragments were inactive as well.

Animals↗
PubMed1985

[Oxygen supply of the human small intestine in mechanical ileus].

In 16 patients operated on for mechanically caused ileus and in 12 control patients (cholecystectomy) local PO2 of the small bower wall was determined by means of a multiwire Pt surface electrode constructed by Kessler and Lübbers. The ileus patients showed an increased pulse rate of 110 (90-115) vs 90 (80-110) beats/min and creatinine levels of 1.06 (0.79-1.45) vs 0.80 (0.70-0.88) mg%. (mean, 1.-3. quartile, P less than 0.05). Local PO2 values of the serosal site of the small bowel were significantly reduced in patients with ileus compared to the control group [22.5 (12.5-35) vvs 61.2 (53.0-71.0) torr.] Hypoxia of the bower in mechanically caused ileus could be demonstrated by local PO2 determination and underlines the demand of early decompression.

Blood Pressure↗
PubMed1985

Characterization of a new repetitive sequence in the Dictyostelium discoideum genome.

A repetitive DNA sequence was isolated from a Dictyostelium discoideum genomic plasmid library of BglII-digested DNA ligated to the BamHI site in pBR322. This clone, called pBS582, hybridized to a large number of phage lambda Dictyostelium genomic clones. Southern blot analysis indicated that pBS582 DNA hybridized to many differently sized genomic DNA fragments generated by digestion with Eco RI, AvaI, or HindIII. Restriction maps of pBS582 and five genomic clones showed that the flanking regions of each of the genomic clones were different. These findings indicate that the sequence specific to pBS582 is scattered throughout the Dictyostelium genome and is reiterated approximately 100 times in the haploid genome. Northern blot analysis revealed that RNA which hybridized to pBS582 DNA was present during all stages of growth and development and did not seem to be developmentally regulated. Southern blot analysis of DNAs from other slime molds (D. giganteum, D. purpureum, and Polysphondylium violaceum) were performed to determine whether the pBS582 sequence was present in other species of slime molds. Hybridization of pBS582 was observed to DNA from the two Dictyostelium species but not to Polysphondylium. It may thus be possible to use hybridization of specific sequences as a biochemical tool to study the relatedness of different slime mold species and their molecular taxonomy.

Bacterial Proteins↗
PubMed1985

[Use of "fermosin" fodder yeast in a multi-generation experiment with chickens. 1. The rearing period].

The use of 5%, 7.5% and 15% 'fermosinR' torula yeast as a reference protein for soybean oilmeal and fishmeal was tested under toxicologic aspects in a multi-generation experiment over 3 generations with small chickens and young hens of the species White Leghorn at the ages of between 5 and 147 days. Only with a quota of 15% 'fermosinR' was the feed and energy consumption of the young animals diminished. Crude protein and amino acid consumption increased with the growing concentration in the mixed feed. For the parameters live weight development and mortality of the young hens no significant relation to the arrangement of the experiment could be proved. The results show that the feeding of 'fermosinR' torula yeast to small chickens and young hens is basically possible. The clinical status ascertained, the results of biochemical investigations and the findings of pathomorphology from the reared animals respectively those died during the experiment are to be reported on.

Age Factors↗
PubMed1985

[The use of "fermosin" fodder yeast in a multigeneration experiment with hens. 2. The laying period].

In a multi-generation experiment with 120 hens of the species White Leghorn per group kept in cages, the influence of 5%, 7.5% and 15% 'fermosinR' torula yeast in the ration of mixed feed on various performance parameters in the 364-day laying period was investigated under long-term toxicologic aspects. In all probability there is no indication of toxic influences. The compatibility of the biomass can be considered good provided the basic nutrition-physiologic demands are met.

Animals↗
PubMed1985

[Use of "fermosine"--fodder yeast in a multi-generation trial with chickens. 3. Evaluation of health safety in a long-term toxicologic test].

In a 3-generation experiment with a total of 2520 hens and 210 cocks of the species 'White Leghorn' kept in cages, the compatibility of 5.0%, 7.5% and 15% 'fermosin' torula yeast in the mixed feed ration was tested under long-term toxicologic aspects. The parameters investigated and relevant for the toxicological statement, with high probability, did not show a negative influence of the test ration. Thus, a good compatibility of the tested yeast product 'fermosin' for laying hens can be stated.

Animal Feed↗
PubMed1985

Aggregation and fibril formation of plasma fibronectin by heparin.

The precipitation of plasma fibronectin by heparin in dependence on various parameters was investigated. Rising heparin concentration augmented the precipitates up to a maximum beyond which precipitation decreased. Yields close to 80% were obtained at low temperatures, but some precipitation was observed at 37 degrees C as well. Insolubilization was considerably dependent on the ionic strength, indicating that electrostatic forces play a major role in the aggregation of fibronectin. Calcium already prevented precipitation by heparin at low concentrations. If precipitation was performed on hydrophobized glass cover slides, the formation of fibrils visible by phase-contrast microscopy was observed. On hydrophilic surfaces amorphous precipitates were generally obtained, most likely due to trapping of aggregates by adsorption prior to their arrangement to fibrils. The results are discussed on the basis of a model assuming that heparin induces a conformational rearrangement of plasma fibronectin so that masked binding sites responsible for self-association become exposed.

Calcium Chloride↗
PubMed1985

Different susceptibility of inter- and intra-chain disulfide bonds to reductive cleavage in native fibronectin and effect of their cleavage on conformation.

The two thread-like subunits (Mr approximately equal to 250 000) of the multidomain protein fibronectin are connected by a pair of inter-chain disulfide bridges in their C-terminal regions. In addition each chain contains 29 intra-chain disulfide bonds which are located in 12 type I and 2 type II structural domains in the N-terminal and C-terminal regions of the strands. The 15 to 17 type III domains in the central portion of the strands do not contain disulfide bonds. The susceptibility of inter-chain disulfide bonds to 10mM 1,4-dithiothreitol at pH 7.8 as quantitated by the rate of reductive cleavage of fibronectin into its subunits was found to be only 8-fold larger than that of the intra-chain bonds. Consequently at 90% completion of chain separation 30% of the intra-chain disulfides are also cleaved. The rate of inter-chain disulfide cleavage was found to be identical for fibronectin and a 140-kDa fragment comprising the C-terminal portions of the two subunits. This shows that the relatively high protection of the inter-chain disulfide bonds must originate from interactions between C-terminal domains which are probably also responsible for the V shaped arrangement of the two subunit strands. Changes of circular dichroism and thermal transition profiles for fibronectin and its C-terminal 140-kDa fragment indicated that already partial reduction of the intra-chain disulfide bonds alters the conformations of type I and II domains without affecting the type III domains.(ABSTRACT TRUNCATED AT 250 WORDS)

Circular Dichroism↗
PubMed1985

[Liposomes from hydrogenated egg yolk lecithin].

Egg yolk lecithin is a lipid, frequently been used for the liposome preparation. Such liposomes, however, are sensitive to oxidation and relatively permeable to encapsulated substances. The catalytic hydrogenation of egg yolk lecithin is one possibility to modify the properties mentioned. The authors deal with preparation and characterization of hydrogenated egg yolk lecithin. Liposomes from native and hydrogenated egg yolk lecithin--also in combination with cholesterol--are compared. Liposomes with hydrogenated egg yolk lecithin as phospholipid component exhibit a significantly increased encapsulation capacity and an essentially improved stability. The permeation of electrolytes, carboxyfluorescein and of the cytostatic drug daunorubicin is studied.

Animals↗
PubMed1984

Evidence for a cryptic lectin site in the cell-binding domain of plasma fibronectin.

Various proteolytic fragments from the central region of the fibronectin subunit chains containing the main cell-affinity site were applied in cell binding studies using peritoneal macrophages of guinea pigs. A 125I-labelled 23-kDa peptide was relatively well bound by the cells. Attachment to cells was partially inhibited by wheat germ lectin, suggesting a lectin-like site in the cell-binding domain which recognizes oligosaccharide groups with terminal N-acetylglucosamine or N-acetylneuraminic acid. Binding was inhibited by N-acetylneuraminic acid with half-maximal effect at 2 X 10(-3) M. Other inhibitors were a sialic acid rich ganglioside preparation and fetuin, a sialic acid-containing glycoprotein. In contrast to the 23-kDa peptide a 125I-labelled 125-kDa fragment was only weakly bound, although it included the sequence of the 23-kDa peptide on its C-terminus. The residual binding was weakly inhibited by low concentrations of wheat germ lectin and was remarkably improved by higher concentrations. The behavior of the peptide was explained by the presence of a sialic acid-containing oligosaccharide side chain localized outside of the 23-kDa region and interacting with the lectin-like site in the cell-binding sequence. In accord with this suggestion a 95-kDa fragment representing the oligosaccharide-containing part of the 125-kDa peptide was capable of inhibiting at least partially the cell attachment of the 23-kDa piece. The results indicate a lectin-like affinity site in the cell-binding region of fibronectin which is accessible in the 23-kDa peptide, but is masked in the 125-kDa fragment and in fibronectin by a sialic acid-containing oligosaccharide moiety.

Cathepsin D↗
PubMed1984

Naloxone decreases centrally induced hyperglycemia in dogs. Evidence for an opioid role in glucose homeostasis.

Intracerebroventricular (ICV) instillation of morphine and beta-endorphin causes centrally induced hyperglycemia. Locally active, endogenous opioids in the central nervous system may, therefore, also be involved in the elevation of blood sugar. This possibility was tested by examining the glucoregulatory response to central glucoprivation induced by ICV administration of 2-deoxy-D-glucose (2DG) in dogs. Administration of 2DG resulted in a rise in plasma glucose and immunoreactive glucagon (IRG) of 108 +/- 19 mg/dl and 70 +/- 20 pg/ml, respectively. These changes were attenuated by the simultaneous central infusion of the opiate antagonist naloxone: plasma glucose levels increased by 77 +/- 14 mg/dl and IRG by 43 +/- 3 pg/ml, both significantly different from the effect of 2DG alone (P less than 0.05-0.01). These findings suggest that opiate receptors participate in the counterregulatory response to central glucoprivation. They also provide a mechanism by which endogenous opioid peptides may play a role in the central regulation of glucose homeostasis.

Animals↗